Hid Lighting Capacitor

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domnic

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Electrical Contractor
I have a metal halide light that calls for a 6 Mfd capacitor if i install a 7.5 Mfd cap. what affect will this have on the lamp and ballast.will the lamp burn brighter? will it change open circuit voltage. will it change the ballast amps ?
 
Not sure why you wouldn't just use the right cap. They should be local stock someplace. Motor shops and HVAC supply houses are places that stock lots of caps. You can safely replace a cap with a different value if it's within 10% on a motor, but I have no idea about ballasts. Not sure I'd even try.
 
mdshunk said:
Not sure why you wouldn't just use the right cap. They should be local stock someplace. Motor shops and HVAC supply houses are places that stock lots of caps. You can safely replace a cap with a different value if it's within 10% on a motor, but I have no idea about ballasts. Not sure I'd even try.
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I forgot why, but they should be matched...
 
The purpose of a capacitor in an HID circuit is to limit lamp current. An operating HID lamp offers very little impedance, so something must limit it. The capacitor is tuned to the ballast and lamp combination, if you change its value, you'll change lamp current as well.

I you do this, you'll become what I term a 'non-compensated test engineer'.

You could measure lamp current with both capacitors, if it doesn't vary much (10%, as a guess), you'll be ok.
 
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